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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

What has global warming done since 1998?

What the science says...

For global records, 2010 is the hottest year on record, tied with 2005.

Climate Myth...

It hasn't warmed since 1998
For the years 1998-2005, temperature did not increase. This period coincides with society's continued pumping of more CO2 into the atmosphere. (Bob Carter)

No, it hasn't been cooling since 1998. Even if we ignore long term trends and just look at the record-breakers, that wasn't the hottest year ever. Different reports show that, overall, 2005 was hotter than 1998. What's more, globally, the hottest 12-month period ever recorded was from June 2009 to May 2010.

Though humans love record-breakers, they don't, on their own, tell us a much about trends -- and it's trends that matter when monitoring Climate Change. Trends only appear by looking at all the data, globally, and taking into account other variables -- like the effects of the El Nino ocean current or sunspot activity -- not by cherry-picking single points.

There's also a tendency for some people just to concentrate on surface air temperatures when there are other, more useful, indicators that can give us a better idea how rapidly the world is warming. Oceans for instance -- due to their immense size and heat storing capability (called 'thermal mass') -- tend to give a much more 'steady' indication of the warming that is happening. Records show that the Earth has been warming at a steady rate before and since 1998 and there is no sign of it slowing any time soon (Figure 1). More than 90% of global warming heat goes into warming the oceans, while less than 3% goes into increasing the surface air temperature.

Even if we focus exclusively on global surface temperatures, Cowtan & Way (2013) shows that when we account for temperatures across the entire globe (including the Arctic, which is the part of the planet warming fastest), the global surface warming trend for 1997–2012 is approximatley 0.11 to 0.12°C per decade.

SirNubwub You are making a common error in interpretiing a statistical statement. "no [statistically] significant warming in the last 15 years" does not mean that "that temps have remained level for the last 15 years".

If a trend is not statistically significant, this means that there isn't enough evidence to be able to confidently reject the possibility that the actual trend is flat. However, evidence requires data and if the timespan over which you estimate the trend is sufficiently short, the test for statistical significance will fail to reject this "null hypothesis" even when it is incorrect.

Essentially if the trend is not significant, then there are two explanations (i) the trend actually is flat or (ii) there isn't enough data. This is why climatologists use 30 year trends, as these are long enough for the test to be statistcally meaningful.

I suspect the paper is referring to a BBC interview with Prof. Phil Jones, where he agreed that the 15 year trend was not statisticlly significant (I think that is no longer true), and also had a go at explaining why this is not surprising.

SirNubwub, there are claims by the Daily Mail. They are based on the press release by the Met Office which shows no increase in temperature on HadCRU figures over the period 1997-2011, but the press release also shows GISTEMP, GHCN, and WMO figures which all show an increase over that period. Ergo, the Daily Mail, by choosing just one of four data sets that suites their narrative are cherry picking. What is worse, it is known that HadCRUT is about to be updated by including more station data, thus reducing some of their gaps in coverage. In the updated HadCRUT, 2005 and 2010 are both warmer than 1998, and there is a distinct positive trend over the period 1997-2011. In other words, not only have the Daily Mail cherry picked, they have cherry picked a data set which is known to be inaccurate compared to the others, and which is about to be supplanted.

I discussed this in more detail here. As the moderator indicates @149, the Daily Mail's intellectual integrity as shown by that article cannot be accurately described on SkS due to the comments policy.

P.S. I could only bring myself to read the first few paragraphs of the newspaper report, but they were enough to show that the problem is that Mr Rose is not competent to be writing articles on this topic, and would benefit from reading a few SkS articles.

SirNubwub, actually that is rather the point. There isn't any 'original paper/press release'. The Daily Mail took the latest updates of the CRU temperature data and NASA solar readings as 'foundation', but all the 'conclusions' they draw came from other sources entirely.

DB, the only way to provide "definitive proof" for my position (i.e. that no such statements from CRU/NASA exist) would be to review all statements from those organizations. However, given that we have seen the 'no warming since XYZ' and 'it is the Sun' nonsense over and over and over and over again it doesn't really seem like a stretch to say, 'no, that tripe did not come from NASA or the CRU' without extensive documentation of all NASA/CRU statements.

In truth, if you read very carefully, The Daily Mail does an adequate job of differentiating between the data from CRU and NASA and the 'conclusions' deniers outside those organizations draw from them.... except for the claim in the article title that, "if NASA scientists are right the Thames will be freezing over again". NASA didn't say anything about the Thames... that's all Rose. Also, SirNubwub's statement that, "NASA and CRU have stated that there has been no significant warming in the last 15 years", demonstrates how easy it is to miss the transitions in Rose's article from things said by NASA and CRU sources and those said by deniers.

Dikran Marsupial @153, in this case it is no warming. The 1997 and 2011 figures are identical in the press release, and 2011 is actually colder than 1997 in the actual data. More importantly the HadCRUT3v trend from 1997 to 2011 inclusive is 0.01 degrees C per decade.

Of course, as shown by Foster and Rahmstorf, once short term independent factors such as volcanoes, the El Nino Southern Oscillation and the Solar Cycle are accounted for, the HadCRU trend from 1997 is > 0.1 C per decade, and is statistically indistinguishable from the long term trend of 0.17 C per decade:

Tom, I wouldn't use the temperature of the start and end point as a reliable indicator of the trend. An OLS trend can show warming even when the start point is warmer than the end point, because individual years are sensitive to ENSO etc.

Dikran, the nature of David Rose's opus is clearly revealed by the fact that he found the time to interview 5 AGW deniers, but not one mainstream climate scientist. Nor did he find the time to interview any of the authors of paper on which he supposedly based his article, and which his article directly contradicts. That is not journalism, except in that very broad sense in which Pravda practiced journalism, and Madison Avenue is the center of Journalism in the USA.

With regard to press releases, etc., this is the original Met Office Press Release (supposedly sneaked out, according to Rose of the Mail), about the paper in question (which was also sneakily referred to here by the Met.
The abstract of the paper itself is available here. No doubt Rose would reckon that was sneakily published too.

The Met Office's correction to the Mail is available here. Shame not too many Mail readers will get to see it, though...

SirNubWub @162, if you are going to show they article as an example of poor journalism, you should highlight the following poor journalistic practices:

1) Failure to report the consensus scientific opinion.
In journalism, assuming the truth of political far from consensus opinions, such as, for example, those held by the communist party, is considered bad journalistic practice. In science this attitude is well and truly justified in that theories reach consensus support based on overwhelming empirical success relative to other candidate theories.

2) False balance.
In journalism, balance is assumed to require giving equal voice to opposing political opinions, but only opinions held within mainstream political parties are sort out. This can be justified on the basis that balance should be proportionate to the relative support of the opinions. In science, however, the relative support must be the relative support among scientists expert in the field. "Balance", therefore would require reporting of opinions in proportion to their relative support (in this case) among climate scientists.

3) Failure to report a balance of veiws at all.
Indeed, rather than simply falsely balancing scientific opinions, the paper reports the views of five climate change deniers, but fails to report the views of mainstream climate scientists (even though we now know that they were provided by the Met Office).

4) Failure to report the provenance of opinions reported.
The climate change deniers whose opinions where sort where not identified as climate change deniers in the article. By doing so the author has taken away from the reader the right of judging the trustworthiness of his sources by depriving them of obviously relevant information.

5) Cherry Picking of Data
Obviously.

You could also point out that Rose has a track record of writing propaganda in preference to pursuing journalism, as reported by George Monbiot and Tim Lambert.

1. Is it perhaps time to update some of your graphs many of which end around 2007?
2. Do you not feel that the Foster and Rahmstorf analysis is compromised by the fact that they assumed a linear trend? ("The influence of exogenous factors will be approximated by multiple regression ... and a linear time trend"). They then derived the coefficients that came closest to that hypothesis. On my own web site for fun I've done a similar analysis for the period 1998 to 2011 and 'proved' that the trend is completely flat for that period. Adjusted temperature 1998 to 2011

RonManley @168, climate models predict non-linear trends that still approximate to linear trends over short intervals (30 years or less). Therefore, the easiest test to falsify the climate model projections in the short term is does the temperature record depart significantly from a linear trend approximating to the model predictions over that short term.

In order to falsify those projections, you would need to do two simple things:

1) Show that a statistically significant and robust short term trend lies outside the significance interval of a trend approximating to that of the predictions; and

2) Show that the assumed conditions of the projections in fact held over the period in question.

Fake skeptics have repeatedly drawn attention to short term trends which are not statistically significant. What is more, they are not robust. The are not duplicated across all temperature indices (for instance), and they change significantly with small changes in start and end point. Therefore they have not shown (1).

Never-the-less Foster and Rahmstorf jumped ahead and tested (2). They showed that conditions did vary significantly from those assumed by the model projections, due to the coupling of several strong La Ninas with an exceptionally weak period of insolation. Further, the showed that if you correct for those factors, the trend is well within the confidence interval of the projected model trends.

The use of the linear trend in that context is unexceptional because of the hypothesis they were testing.

s0nathan I suspect the response for the first figure would be to ask for it to be plotted again, this time showing the uncertainty on the observations and the spread of the model runs (which is an indication of the uncertainty in the projection). For the second image, try this article.

abstract: "We review the sea-level and energy budgets together from 1961, using recent and updated estimates of all terms. From 1972 to 2008, the observed sea-level rise (1.8 +/- 0.2 mm yr(-1) from tide gauges alone and 2.1 +/- 0.2 mm yr(-1) from a combination of tide gauges and altimeter observations) agrees well with the sum of contributions (1.8 +/- 0.4 mm yr(-1)) in magnitude and with both having similar increases in the rate of rise during the period. The largest contributions come from ocean thermal expansion (0.8 mm yr(-1)) and the melting of glaciers and ice caps (0.7 mm yr(-1)), with Greenland and Antarctica contributing about 0.4 mm yr(-1). The cryospheric contributions increase through the period (particularly in the 1990s) but the thermosteric contribution increases less rapidly. We include an improved estimate of aquifer depletion (0.3 mm yr(-1)), partially offsetting the retention of water in dams and giving a total terrestrial storage contribution of -0.1 mm yr(-1). Ocean warming (90% of the total of the Earth's energy increase) continues through to the end of the record, in agreement with continued greenhouse gas forcing. The aerosol forcing, inferred as a residual in the atmospheric energy balance, is estimated as -0.8 +/- 0.4 W m(-2) for the 1980s and early 1990s. It increases in the late 1990s, as is required for consistency with little surface warming over the last decade. This increase is likely at least partially related to substantial increases in aerosol emissions from developing nations and moderate volcanic activity."

s0nathan - climate models do not anticipate La Nina & El Nino to suddenly disappear, so clearly the figures in your post are wrong - surface temperatures are not expected to increase in a straight line.

Note how the observations are still within the range of the IPCC climate model ensemble. And also check out figure 1 in my comment @170. The ocean heating rate and TOA (top-of-the-atmosphere) radiation flux fall within the simulations of the 15 climate models used there.

sOnathan @171, I recommend to you the two excellent replies by Chris and Rob Painting (and Dikran's sage advise). As they have covered much of the territory I would have, I will try to restrict my comments to points they have not already covered.

1) Ocean Heat Content

The obvious point here is that David Evans has picked a high point in the data as his start point, thereby artificially increasing the apparent discrepancy between the data and the models. This is made obvious by comparing the graph shown by David Evans with that shown by Rob Painting. Evans justifies his start point by saying,

"We’ve only been measuring ocean temperature properly since 2003, using the ARGO system."

That claim is simply false. Prior to Argo, a number of different methods where used to measure ocean heat content, of which the largest was the XBT in which over 5 million eXpendable BathyThermographs were deployed from the 1960s onwards. They do not give perfect information, but imperfect information is not the same as no information. The habit of ignoring imperfect information because it does not tell you what you want to here is, to put it mildly, not scientific.

What is more, the Argo program was not yet extensive enough in 2003 to give significantly improved data compared to the XBT program:

It is only in 2006 that it became an effectively global program. But had Evan's zeroed the curves in 2005 or 2006 it would not have told the right story, which I guess is exactly the point.

2) Hansen's 1988 predictions

You have to wonder why Evans chooses to focus on a 1988 model when computing power was to crude for the model to include aerosols, a known significant factor, instead of on later models from the 2001 IPCC report, or the 2007 IPCC report. This is particularly the case because Hansen's predictions are known to be wrong, and are predicted to be wrong by the global warming community. This is primarily because the forcing factor of CO2 was determined in 1998 to be overstated by 18%. Therefore, as a criticism of AGW, Evans' blogpost is fourteen years out of date.

More concerning is Evans little edit to the 1988 forecast graph indicating that scenario A is what happened. For reference, here is a comparison between actual 2010 GHG concentrations and Hansen's scenario B projections for 2010:

To be fair, Hansen's scenario A projection for CO2 was 391.5 ppmv, which is pretty close. But CO2 concentrations where well less than Hansen's scenario A projections in the 1990s due to the collapse of the Soviet Union, and caught up again in the 2000s due to the rapid industrialization of China. The net effect is that on average the CO2 forcing was well below the Scenario A projection, and because of thermal lag, it is the earlier (and lower) part of that projection which has the most significance for current temperatures. It should also be noted that NO2 concentrations and CFC 12 concentrations are less than Hansen's scenario C projections.

Overall the effect is as if GHG concentrations had tracked just below Hansen's scenario B. The interesting question to ask Evans is, why did he state Scenario A is what happened, and how did he check? The answer, as it cannot have been a thorough check will reveal that what he is doing is not science, but propaganda.

This is also shown by his use of the HadCRUT3 temperature index, which is known to have less than global coverage, which is known to create inaccuracies. What is more, it is also known that it is obsolete and is about to be replaced by HadCRUT4, which like GISTEMP shows 2010 as being hotter than 1998. That would lift the end point of the temperature graph to just below Hansen's scenario B projection. Given the actual development of GHG concentrations, that's not such a bad projection, but of course, again, its the wrong story.

I notice Evan's finishes with a call for a debate. Well, apparently unknown to Evans, there is an actual scientific debate about AGW that goes on in the scientific literature. Unfortunately for Evans, in that debate you are required to handle your data with integrity, which it would appear would leave Evans shooting blanks. In fact, the stunning dearth of "skeptical" voices in the scientific literature really seems to come from that one requirement.

Until so-called skeptics actual start publishing their theories in respectable, climate oriented scientific journals, the proper assumption is that they cannot because their argument evaporates when you are required to handle data with integrity. It therefore follows that on climate they really have nothing interesting to say.

I'm sure you'll do a blog entry on this in due course, but in the meantime here is a link to a report on the update to HadCRUT, which now has 2010 as the hottest year on record, rather than 1998, bringing it into line with NASA and NOAA

Not that a sign of increasing temperature proves that humans are causing it, but just dealing with the argument..

The article starts with a straw man logical fallacy "No, it hasn't been cooling since 1998." implying that was Carter's position. No warming doesn't imply cooling.

According to the latest HadCRUT4 data, there is no statistically significant increase in temperature (0.083C/dec +/-0.172C/dec). It is also stressed in the HadCRUT4 report that it cannot be said yet whether 2005 or 2010 are the hottest on record.

hutch44uk
given that such a short trend does not give as an answer, try to ask yourself the question the other way around, do we have reason to belive that the trend has stopped or even slowed down? The answer is no, both statistically and climatologically.

"Remembering that the radiative effects of extra carbon dioxide occur at the speed of light, and that both the ocean and the atmosphere are currently cooling, just where is this 0.5°C. of "pipeline" heat supposed to be hiding?)."

However, it is one that is heard a lot in these parts. Given the generally intended meaning is that 1998 was warmer than xxxx, we have a very good explanation here. If nothing else, that exercise will help you learn how to connect the dots more appropriately.

Hutch44UK "no statistically significant warming" doesn't mean that there is no warming. It means that the trend is too small in magnitude relative to the noise that we can't rule out the possibility that it isn't warming.

If you want to use a lack of statistical significance to establish that it hasn't been warming then you would need to show that the statistical power of the test was sufficiently high that a statistically insignificant result would be a surprise if the trend actually was of continuing warming at the same rate as before.

Alternatively you could try to show that the change in trend since (say) 1998 was statistically significant.

Needless to say, skeptics generally don't do this and instead are happy to misuse statistical tests.

Since your 'first claim' was that this article starts with a strawman - and that is incorrect - you do indeed need answer no questions (none were asked of you).

As to your subsequent claim of 'no statistically significant increase in temperature,' take out the ENSO noise and you're once again incorrect. Since you reference Foster and Rahmstorf 2011, perhaps you should note their very clear statement:

there is no indication of any slowdown or acceleration of global warming, beyond the variability induced by these known natural factors.

Then check Nielsen-Gammon, who also shows a consistent increase in temperatures. Apples to apples comparisons make sense, don't they?

But if you insist on comparing el Nino years with la Nina years, why have recent la Ninas been warmer than the prior el Ninos?

hutch44uk I am not questioning what the trend calculator says. I am pointing out that a particular intepretation often used by skeptics is incorrect.

A lack of statistically significant warming does not mean it is not warming, just that you cannot rule out that possibility.

If you have a two headed coin and flip it four times and get a head each time (oddly enough) then the usual test for the coin being biased gives the result "no significant". Does that mean the coin is fair? No, of course it doesn't, the coin has a head on both sides! The reason you get a result of "not significant" is that there have been too few coin flips observed to rule out the possibility that the coin is fair (at the usual 95% significance level).

BTW if you adopt a statistic to make an argument, then they are your statistics, if only by adoption. You need to be able to defend your use of them, whether you calculated them or not.

hutch, one of the things you are apparently not understanding is the difference between 'true' and 'meaningful'. It is true that there has been no statistically significant trend since 1998... it just isn't at all meaningful.

There have been 13 years since 1998. If you look at the entire temperature anomaly record you will find very few (possibly zero) cases where a statistically significant trend occurred over a period of just 13 years. You are citing a period too short to achieve statistical significance as if it told us something about the trend. It does not.

Essentially, you are pressing your nose up against a tree (i.e. the statistically insignificant past 13 years) so hard that you cannot see the surrounding forest (i.e. the rising temperature trend) and thus are 'free' to continue pretending it does not exist... [snip]

Surface temperatures are but a small portion of the global warming picture. Over 90% of global warming goes into the oceans (amply documented on this website). In addition global warming is itself but the result of a radiative energy imbalance whereby the Earth retains more energy than it emits - the Earth climate system is then forced to warm up to increase emissions to match, as per (as far as I know) undisputed principles of thermodynamics.

As long as one can demonstrate the following:
(1) There remains a measured top-of-atmosphere energy imbalance (conventionally measured as a forcing in Watts per square metre), and
(2) The oceans continue to build up heat energy (conventionally measured as ocean heat content, in Joules),
then there is simply no basis to conclude that global warming has in any way stalled or stopped, whatever variations show up in short-term surface temperature data.

If you have sources showing both (1) and (2) are no longer operative, please feel free to share.

Finally, I should address your accusation of Skeptical Science "moving the goalposts".

From a logic standpoint, the fact of the matter is that the "global warming stopped in 1998" claim, whether asserted baldly or on the basis of no satistically-significant warming, is a cherry-pick. As such, dismantling the cherry-pick by including additional relevant information does not IMO constitute a shifting of goalposts.

muoncounter, "take out the ENSO noise, and you're once again incorrect". The argument wasn't about warming purely from non-ENSO sources. Stop changing my position please!

Dikran, no they're not my statistics. Foster and Rahmstorf chose a 2-sigma error band for statistical signficance, not me.

CBDunkerson, it seems you agree with me by admitting it's true. I agree with you too.. this whole argument isn't at all meaningful, as it doesn't prove that CO2 is causing the warming anyway (for another thread)!

hutch, your first claim (Carter did not claim cooling) has been refuted by Tom @ 180. Do you acknowledge this?

Your second point has been amply responded to: within a specific set of dates, no significant warming (which, as you point out, doesn't mean cooling) can be demonstrated when using a chosen data set for a specific part of the atmospheric system (more specifically the part that doesn't store the greater part of the energy) and using a particular type of analysis that doesn't account for particular types of forcings.

What you could possibly use this result for, I can't imagine. Well, I can imagine, but I'd rather give your integrity the benefit of the doubt before going there.

1) Do you agree that the trend shown by HadCRUT4 from 1970 to current is 0.172 ±0.033 °C/decade (2σ)?

2) Do you agree that that is a statistically significant warming?

3) Do you agree that the HadCRUT$ trend from 1998 to current is 0.083 ±0.172 °C/decade (2σ)?

4) Do you agree that the 1998 to current temperature trend shows no statistically significant difference from the 1970 to current trend?

5) Do you agree that the 1998 to current trend shows no statistically significant difference from the IPCC prediction for the current decade of 0.2 °C/decade?

6) Do you agree it is incorrect to interpret "no statistically significant warming" as meaning "no warming" given your answers to the above questions?

7) Do you agree that choosing 1998 (or any point in the half decade before 1998) as a start point for a temperature trend, by including a very strong El Nino in the early part of the record, and a sequence of moderate to strong La Nina's in the later part of the record, maximizes the noise relative to the signal and hence constitutes a "cherry pick" if you attempt to draw a conclusion of "no warming" from that data?

Given the propensity of fake "skeptics" to simply go silent when their meme is refuted, readers can reasonably interpret your failure to answer the above questions as showing that you have been attempting to sow confusion on this thread.

DSL @189, I have not strictly refuted the contention of a strawman argument. It is logically conceivable that when Carter claims the atmosphere is cooling in the quote I provided that he refers only to the period from early 2010 to 2011, ie, to a period featuring a transition from a moderate El Nino to a strong La Nina.

What I do show is that Carter has said things which do imply a cooling atmosphere. Without referencing the original article, it is impossible to say whether or not Carter claimed that it was cooling from 1998 to 2006. Of course, without referencing that article, hutch44k has no basis to claim that the OP argues a straw man. Fortunately I have now found Carter's original article, and find that he wrote that "[T]here was actually a slight decrease [in temperature recorded by the HadCRUT3 index], though not at a rate that differs significantly from zero".

On the purely technical point, Carter's claim about HadCRUT3 appears to have been wrong in 2006. The warming shown on the trend calculator from 1998-2005 is 0.065 ±0.482 °C/decade (2σ). Of course, that used HadCRUT3v, while Carter refers to HadCRUT3 (which differs slightly), but it appears unlikely that his claim was even technically correct.

Even if it where, it shows the extreme nature of his cherry pick, relying not just on a particular temperature index but on a particular version of that index. It also shows he is using an interval in which the error range in calculating the trend is 2.4 times the IPCC predicted trend. No scientist cannot know that such extreme cherry picking, and that data with such large error margins cannot be used to make any valid scientific point.

Tom, I stand corrected to the extent that Carter is being honest and open with regards to the intent of the publication (such as it was) of his analysis. If his dodgy methodology was an honest mistake and not an attempt to force the data into a politically palatable message for his target audience, well I humbly apologize to all involved.

hutch44uk: "The argument wasn't about warming purely from non-ENSO sources."

The argument is about determining whether or not there is continued warming. You choose to start your analysis from an anomaly and that artificial selection allows you to declare there is no statistically significant trend. A more objective analysis would look at all the data. A more informed and thorough analysis would process the data as FR2011 did or separate the signals as Nielsen-Gammon did, in order to detect the underlying trend.

To ignore these analytical methods is to focus on the noise rather than the signal. But focusing on noise is the key component of denial these days, isn't it?

I have recently been in an online discussion on another board with a contributor who tells me he has been crunching NCDC statistics. As a result he believes the 1940s were as warm as today. I've shown him GISS graphs and he's waved them away as based upon extrapolated data. He's been kind enough to post his graphs and charts on science20. In response to the recent news of May11-Apr12 being the warmest 12 months, as recently reported, he has posted http://www.science20.com/comments/107815/John_Samuel_%C2%B7_Says. And, in response to my pointing him to GISStemp data showing an increase from 1940-2010 he posted this, http://www.science20.com/virtual_worlds/blog/2011_5th_warmest_year_decades-87380, I've encouraged him to post himself to see if his findings bear scrutiny. He's demurred. Do any of the gentle readers have any comments?

I would suggest posting direct links to the NCDC online and asking the contributor to explain why the information provided by agency that actually publishes the information he is using stands in such stark contrast to his conclusions.

He should be able to explain how his number-crunching is methodologically superior to the NCDC if he expects his conclusions to be persuasive.

Composer99 & Daniel - thank you both for your responses. I'd pointed him to other data sources and he dismissed them out of hand with comments such as "extrapolation is just guessing". So I've now simply disengaged. He expected me to trawl through is dataset and interpolate his method, but he won't acknowledge the peer-reviewed material. Life's too short. Daniel, your comment about Mike's leanings - I did a Google of his name and variants and some likely qualifying terms - and came up with nothing (unless he runs Arizona U). I've missed summat - how did you reach that very possible evaluation.

The last paragraph of the post from Hutch44uk (#178) below, together with the extensive comment on this thread about evidence and statistical significance, prompts two questions, which hopefully will be discussed by supporters of both sides of the AGW issue.

"hutch44uk at 22:02 PM on 30 April, 2012
Not that a sign of increasing temperature proves that humans are causing it, but just dealing with the argument..

The article starts with a straw man logical fallacy 'No, it hasn't been cooling since 1998.' implying that was Carter's position. No warming doesn't imply cooling.

According to the latest HadCRUT4 data, there is no statistically significant increase in temperature (0.083C/dec +/-0.172C/dec). It is also stressed in the HadCRUT4 report that it cannot be said yet whether 2005 or 2010 are the hottest on record."

Q1. A number of comments emphasise the relevance of a sufficient period of observations, in order to determine trends or stasis. Assuming the HadCRUT4 data referenced above is indeed correct, and assuming the quoted temperature increase and range of error remained constant, after what time would that data become statistically significant?

The next question is wider, given the depth of technical discussion on this thread, but I think very relevant to the AGW issue. While most people rely on formal bodies for direction on scientific opinion (in the case of climate change, on the IPCC and national authorities), it is obvious that many contributors to this thread have the technical knowledge to form their own views independently (while obviously drawing on scientific and other published literature).

Q2. If you have presently reached the conclusion that there is, or is not, significant anthropological global warming (AGW) occurring at present, whose primary mechanism is through the greenhouse gas effect (GHG), what credible data and information over what period would you require (rather than simply some authoritative opinion), for you to change your mind?

I look forward very much to informed comment on these questions, as such will assist me in my own analysis. Thank you.

what credible data and information over what period would you require (rather than simply some authoritative opinion), for you to change your mind?

I'm not sufficiently technically literate to avoid relying on the expert authority.

However, as I noted upthread there are two fundamental elements which at the present time unequivocally demonstrate global warming:
- the ongoing accumulation of heat in the ocean
- the ongoing measured positive energy imbalance at top-of-atmosphere

I expect either or both of these would have to be unequivocally trending negative, over a statistically significant period, before I would expect to see a major shift in position.